import java.util.Scanner;

public class test {
    public static int fab(int n) {
        if (n == 1 || n == 2) {
            return 1;
        } else {
            return fab(n-1) + fab(n-2);
        }
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        System.out.println(fab(n));
    }
}
